One of the most compelling future uses for biotechnology is the generation of hybrid organic-inorganic devices that could carry out biological functions. Applications for such devices are numerous. For example, they could be implanted and perform diagnostic or therapeutic functions, such as supplying needed enzymatic activities or releasing drugs to specific tissues. These devices could circulate within the blood and release a drug or catalyze a reaction upon stimulation by exposure to a specific molecule, pathogen, diseased cell, or tissue type. They might even enter into single cells where they could compensate for a defective or absent biological reaction. Alternatively, they could perform mechanical functions as “nanobots.”
Examples of nanoparticle delivery vehicles exist in the art (U.S. Pat. No. 7,332,586 and U.S. Patent Application Publication No., 2008/0199529 to Franzen et al.). However, the applications of a self-powered organic-inorganic device that can carry out biological functions is much more extensive. For example, a hybrid organic-inorganic device which performs biological functions could carry enzymes to replace missing functions, such as a congenital defect where a patient is born without a specific enzyme. This would present an alternative to “gene therapy” in which the patient's DNA has to be altered. Alternatively, one could potentially use such a device to carry an enzyme capable of degrading a toxin or recognizing and destroying a pathogen. Another potential function would be to create a device that could bind to either pathogens or cancer cells, and then specifically pump out a drug or metabolite directly at that cell. Similarly, one could create a device that a surgeon might pack into an infected wound to pump out an antibiotic in an area with poor vascularity. Both approaches would increase the local concentration of that drug and decrease systemic toxicity. However, the problem of how to power such devices—particularly on a very small, nanometer scale—remains a critical obstacle to the development and practical use of such devices.
Examples of hybrid organic-inorganic nanodevices have been reported. For example, a recombinant F1-ATPase has been produced that is tethered to a solid surface on one end and supports a small nickel rod on the other end (Soong et al., “Powering an Inorganic Nanodevice with a Biomolecular Motor,” Science, 290:1555-8 (2000)). Soong demonstrates that upon hydrolyzing ATP (the most common form of cellular energy for biological reactions), this molecule undergoes a rotary motion and the rod can be seen to move. An “on-off switch” in the form of a reversible binding site has been engineered into this same molecular motor (Liu et al., “Control of a Biomolecular Motor-powered Nanodevice with an Engineered Chemical Switch,” Nat. Mater., 1:173-7 (2002)), showing that such devices can be regulated. Similarly, other manometers are based on RNA helicases, kinesins, dyneins, or myosin. However, to be functional, ATP must either be provided exogenously or produced locally at the device itself.
A system to generate ATP has been reported, using bacteriorhodopsin and the F0F1-ATP synthase (Luo et al., “Photo-Induced Proton Gradients and ATP Biosynthesis Produced by Vesicles Encapsulated in a Silica Matrix,” Nat. Mater., 4:220-4 (2005); Choi et al., “Advances in Nano Biotic/Abiotic Hybrid Systems: Protein-Based Engineered Devices,” Nanobiotechnol 3:66-75 (2007)). However, this system requires exogenous light which is not practical for in vivo medical applications.
A second example of a nano-biomachine was created from microtubules and hetero-bifunctional polymer particles bearing pyruvate kinase, which is propelled on glass surfaces coated with kinesin by use of self-supplying ATP (Du et al, “Motor Protein Nano-biomachine Powered by Self-supplying ATP,” Chem Commun., 2080-82 (2005)). However, this nano-machine is directed to use in vitro for motility assays with microtubules that travel over glass surfaces. It requires, not glucose or fructose as a starting material, but exogenous adenosine diphosphate (“ADP”) and phosphoenol pyruvate (“PEP”) to produce ATP.
Attaching or linking proteins to a solid support is well-known in the field. However, maintaining the activity of a protein coupled to a solid support has challenged scientists in the field, and only a few instances of linking a single protein to a solid support and maintaining the activity of that protein have been shown.
The present invention is directed to overcoming these and other deficiencies in the art.